Pump control system

ABSTRACT

A pump controller is disclosed for controlling a pump for a fluid medium such as water. The pump controller includes a metal substrate ( 11 ) adapted to have a first side thereof exposed to the fluid medium and an insulating medium applied to a second side of the substrate. A pressure sensing means ( 12 ) including at least one pressure responsive element (R 9 , R 10 ) is implemented on the insulating medium closely adjacent the substrate such that the pressure element is responsive to pressure of the fluid medium when the first side is exposed to the fluid medium. A flow sensing means ( 13 ) including at least one source of heat ( 15 ) and at least one temperature responsive element ( 16 ) is implemented on the insulating medium closely adjacent the substrate, such that the temperature responsive element is responsive to flow of the fluid medium when the first side is exposed to the flow, with the fluid medium providing a sink for the source of heat in a manner that is related to the flow. The pump controller includes switching means ( 17 ) for switching the pump on or off and a processing means ( 14 ) for receiving data from the pressure sensing means and the flow sensing means. The data is communicated via conductive tracks implemented on the insulating medium. The processing means is adapted to process the data and to produce an output for driving the switching means. A housing for a sensor substrate having a wet side and a dry side and adapted to promote contact of the wet side with the pumped fluid medium and to substantially prevent contact of the dry side with the fluid medium is also disclosed.

[0001] The present invention relates generally to a pump control system.In particular the present invention relates to a sensor assembly for apump control system.

[0002] A simple pump controller for controlling an irrigation,industrial or domestic water pump typically employs a pressure switchwhich is set to operate the pump between low and high pressurethresholds. The switch turns the pump on when the low threshold isreached and off when the high threshold is reached.

[0003] One deficiency of such a controller is that the pump tends tocycle unnecessarily between the two thresholds. When a centrifugal pumpis used, for example, it would be much more desirable to operate thepump continuously until the associated outlet is turned off, sincerunning the pump at maximum pressure is not an issue.

[0004] To achieve this, flow detection has been introduced in some priorart pump controllers in addition to pressure detection. This allows thepump to turn off in the absence of flow but adds considerable complexityto the pump controller and has been achieved with sensors fundamentallydifferent in form. Moreover, such sensors tend to have operating pointsthat need to be manually adjusted in the field to match the output ofthe pump to the requirements of an installation site. In a stand aloneinstallation (ie. an installation to an existing pump system) it isdesirable that the pump controller automatically adapts to any viablecombination of installation and pump.

[0005] Attempts have been made to address the above problems withrelatively simple adaptive systems but the known solutions still allinterrupt the pump causing an undesirable decline in pressure. Onesolution involves measuring the performance of the pump by monitoringclosed head pressure. The controller may determine that pressure isrequired when a predetermined drop in pressure (e.g. 20%) is detectedand may start the pump in response to such drop in pressure.

[0006] The present invention addresses the problem by means of anintegrated sensor system mounted to a metal substrate that is in directcontact with the flow of water or other pumped fluid or medium. Themetal substrate preferably includes a titanium plate. In someembodiments the substrate may include low carbon stainless steel. Thesensor system includes pressure sensing means such as a strain gauge.The strain gauge preferably includes a thick film piezo resistor mounteddirectly onto the dry side of the metal substrate. The sensor systemincludes flow sensing means utilising thermal transfer or lossmeasurement techniques. Flow sensing means based on thermal techniquesare described in publicly available documents including WO91/19170entitled “Flow Sensor and Control System”, the disclosure of which isincorporated herein by cross reference. The flow sensing means includesa source of heat such as a heater element and a plurality of temperaturesensors such as thermisters.

[0007] The heater element and the or each thermister may be printeddirectly onto the dry side of the metal substrate utilising thick filmtechnology. A control unit for controlling thresholds and operation ofthe system may be mounted in close proximity to the pressure/flowsensing means such as directly onto the metal substrate.

[0008] The control unit may include a microprocessor or microcontroller.The control unit may have its inputs connected to the pressure sensingmeans and/or the flow sensing means via conductive tracks printeddirectly onto the dry side of the metal substrate. The metal substrateincludes on its dry side, an insulator such as a ceramic to insulate theconductive tracks and other components from the metal substrate.

[0009] Construction of the sensor system onto a common metal substratefacilitates dissipation of heat, typically from the pump switchingelement such as a triac. In some embodiments the triac may also serve asthe source of heat for the flow sensing means, dispensing with the needfor a separate heater element. Construction of sensing elements onto ametal body utilising thick film technology involving printing and firingof dielectric inks is described in publicly available documentsincluding U.S. Pat. No. 5,867,886 entitled “Method of making a ThickFilm Pressure Sensor” and U.S. Pat. No. 6,022,756 entitled “MetalDiaphragm Sensor with Polysilicon Sensing Elements and Methodstherefor”, the disclosures of which are incorporated herein by crossreference.

[0010] A desirable feature of a sensor assembly for a pump controller isthat the assembly functions reliably notwithstanding that it is requiredto interface directly with the pumped fluid medium under pressure. Thepumped medium may present an inherently hostile environment to sensitiveelectronic components. The sensor assembly may be effectively isolatedfrom the hostile environment due to its placement on the dry side of thesensor substrate. However, it is still necessary to ensure that the dryside of the substrate is effectively sealed against ingress of moisturefrom the wet side. The means used for sealing the sensor assemblypreferably is effective in an environment in which fluid pressure causesthe sensor substrate to deflect. Controlled deflection is a desirablefeature of the sensor substrate as this may transmit information aboutthe pressure of the fluid to the pressure sensing means on the dry sideof the substrate. The sealing preferably also should be achievedrelatively economically for a mass produced sensor assembly.

[0011] The sealing means may include at least a first seal element and asecond seal element. The first seal element may include an elastomericmaterial such as a natural or synthetic rubber. The first seal elementmay be adapted to substantially prevent ingress of fluid underrelatively high pressure of the pumped fluid medium. The first sealelement may surround an opening in a sensor housing which communicateswith the pumped medium. The first seal element may include a peripheralbead. The first seal element may be interposed between the wet side ofthe substrate body and a peripheral portion of the housing surroundingthe opening in the housing. The elastomeric material may be chemicallyinert with respect to the pumped medium. The elastomeric material may beat least sufficiently resilient to allow the substrate body to deflectincrementally whilst minimising ingress of pumped medium into thehousing. Because some ingress of medium may be unavoidable, the firstseal element may include a leak path to a first chamber. The firstchamber may be vented to atmospheric pressure. The first chamber may beisolated from the dry side of the substrate body by means including asecond seal element. Venting of the first chamber to the atmosphere mayensure that any high pressure leak drains to the atmosphere before itpenetrates the second seal element which protects the dry side of thesubstrate body.

[0012] The second seal element may include an elastomeric material suchas natural or synthetic rubber. The second seal element may include aperipheral bead. The second seal element may be interposed between aperipheral edge associated with the first chamber and a closure element.The closure element may include a second chamber. The second chamber maybe vented to atmospheric pressure. The second seal element may beadapted to substantially prevent ingress of moisture to the secondchamber. The second seal element may include a resilient wall which canrespond to changes in internal pressure caused by atmospheric conditionsor changes in temperature. The resilient wall may substantially preventingress of damp air (moisture) over time. The second chamber may be incommunication with the dry side of the sensor substrate. The secondchamber may be adapted to house electronic components associated withthe sensor system.

[0013] The first and second seal elements may be interconnected. Theseal elements may be connected by means of a membrane. The membrane maybe formed from the same or similar material as the first and second sealelements or it may be formed from dissimilar material. The membrane maybe formed integrally with the seal elements. The membrane may be shapedto envelop at least the peripheral edge of the substrate body. Thesensor housing and associated closure may include one or more recessesadapted for receiving the first seal element, the second seal elementand the enveloped peripheral edge of the substrate body.

[0014] The housing including the sensor assembly may be interposedupstream or downstream relative to the pump.

[0015] The sensor housing may include a venturi device designed toaccelerate the flow of the pumped medium at least in the vicinity of thewet side of the substrate body. The venturi device may include aformation utilising the venturi principle to convert pressure energyassociated with flow of the pumped medium to kinetic energy, through anarrowed portion of the formation. The venturi device may be located inthe vicinity of an outlet in the sensing housing and may be adjacent theopening in the housing which facilitates communication of the pumpedmedium with the wet side of the substrate body.

[0016] According to one aspect of the present invention there isprovided a pump controller for controlling a pump for a fluid mediumsuch as water, said pump controller including:

[0017] a metal substrate adapted to have a first side thereof exposed tosaid fluid medium;

[0018] an insulating medium applied to a second side of said substrate;

[0019] pressure sensing means including at least one pressure responsiveelement implemented on said insulating medium closely adjacent saidsubstrate such that said pressure element is responsive to pressure ofsaid fluid medium when said first side is exposed to said fluid medium;

[0020] flow sensing means including at least one source of heat and atleast one temperature responsive element implemented on said insulatingmedium closely adjacent said substrate, such that said temperatureresponsive element is responsive to flow of said fluid medium when saidfirst side is exposed to said flow, said fluid medium providing a sinkfor said source of heat in a manner that is related to said flow;

[0021] switching means for switching said pump on or off; and

[0022] processing means for receiving data from said pressure sensingmeans and said flow sensing means, said data being communicated viaconductive tracks implemented on said insulating medium, said processingmeans being adapted for processing said data and for producing an outputfor driving said switching means.

[0023] According to a further aspect of the present invention there isprovided a housing for a sensor substrate having a wet side and a dryside and adapted to promote contact of said wet side with a fluid mediumand to substantially prevent contact of said dry side with said fluidmedium, said housing including:

[0024] a main body having an opening for said fluid medium and forreceiving said sensor substrate with its wet side exposed to saidopening;

[0025] a first chamber maintained substantially at atmospheric pressure;

[0026] first sealing means arranged between said opening and said sensorsubstrate such that a leak path is provided to said first chamber;

[0027] a closure for said housing including a second chamber exposed tosaid dry side of said sensor substrate; and

[0028] second sealing means arranged between said closure and said firstchamber to substantially prevent ingress of said fluid medium to saidsecond chamber.

[0029] To minimize cycling of the pump controller in the face of smallleaks or drips (in a non resilient hydraulic circuit a small drip cancause the pressure to drop significantly) which could trigger anundesirable number of short runs of the pump, it is highly desirable toprovide a leak compensating device such as an accumulator. Theaccumulator may be spring powered and may compensate a minimum quantity(e.g. 30 cc.) of drawn off water or the like. The accumulator may beexternal or it may be integral with the pump controller.

[0030] Alternatively or additionally the processing means may beprogrammed via suitable software adapted to detect small leaks such as adripping tap. In one form the software may interpret a sequence of pumprunning cycles of substantially the same or regular duration as a ‘slowleak’. This may switch the pump to a ‘dripping tap mode’ wherein thepredetermined drop in pressure which causes the pump to start may beincreased from, say 20% to 50%. The greater reduction in pressure mayalso cause the leak to self heal in some instances, avoiding furtherrunning of the pump. This may increase the time between pump runningcycles. The ‘dripping tap mode’ may be implemented for a set period, say2 days, before switching the pump back to its standard operating mode.The software may additionally include a ‘cistern fill mode’. The‘cistern fill mode’ may be implemented if a sequence of short pumprunning cycles is detected in quick succession, say 3 running cycles in45 seconds. In the ‘cistern fill mode’ the pump may be run continuouslyfor say 2 to 4 minutes. The continuous runs of the pump may be repeateduntil the short pump running cycles are no longer detected.

[0031] A preferred embodiment of the present invention will now bedescribed with reference to the accompanying drawings wherein:

[0032]FIG. 1 shows an overview of the sensor system mounted to a sensorsubstrate;

[0033]FIG. 2 shows functional elements associated with the pressure andflow sensing means;

[0034]FIG. 3 shows a schematic circuit diagram of electronics associatedwith the sensor system;

[0035]FIG. 4 is a cross section through the sensor housing showing adouble seal protecting the dry side of the sensor substrate from highpressure fluid;

[0036]FIG. 5 shows the wet side of the sensor substrate mounted within aseal assembly;

[0037]FIG. 6 shows the dry side of the sensor substrate mounted withinthe seal assembly;

[0038]FIG. 7 shows a similar view to FIG. 6 with electronic componentsmounted to the dry side of the sensor substrate;

[0039]FIG. 8 shows the main body of the sensor housing for the sensorassembly with its closure member;

[0040]FIG. 9 shows the underside of the closure member;

[0041]FIG. 10 shows the flow-sensing opening in the main housing whichfacilitates communication of the pumped fluid with the wet side of thesensor substrate;

[0042]FIG. 11 shows the sensor assembly of FIG. 6 fitted to the mainhousing; and

[0043]FIG. 12 shows a venturi device adjacent the flow sensing opening.

[0044]FIG. 1 shows one form of sensor assembly 10 according to thepresent invention. The sensor assembly 10 includes a substrate 11 in theform of a titanium or alternatively a stainless steel plate. Substrate11 includes pressure sensing means 12 and flow sensing means 13implemented directly onto its dry side using thick film hybridtechnology. Pressure sensing means 12 contains four pressure sensingelements including resistors R9, R10 in tension. As shown in FIG. 2deflection of substrate 11 is measured by a change in value due totension of the resistors formed by conductive tracks on substrate 11.Flow sensing means 13 includes heater 15 and temperature sensor 16. Asshown in FIG. 2 flow rate is measured by detecting a measure of heatloss to the body of fluid being pumped adjacent the wet side ofsubstrate 11. Substrate 11 includes microcontroller 14. Microcontroller14 receives inputs from pressure sensing means 12 and flow sensing means13 and is adapted to switch triac 17 controlling pump motor 18. Triac 17is mounted in thermal communication with substrate 11 ensuring gooddissipation of heat due to heat loss to the body of fluid being pumpedadjacent the wet side of substrate 11. In some embodiments heater 15 maybe dispensed with since its role may be performed by triac 17.

[0045]FIG. 3 shows a schematic circuit diagram of one form of sensorassembly according to the present invention. The sensor assemblyincludes microprocessor 30 which may comprise an ST6 familymicroprocessor manufactured by ST Microelectronics. The sensor assemblyfurther includes temperature sensing means shown generally at 31including fluid thermisters R16 and R18 and air thermister R38. Airthermister R38 is adapted to detect ambient temperature of air insidethe enclosure that houses the electronics. Microprocessor 30 isprogrammed to provide a measure of the temperature on the wet side ofthe substrate via thermister R16 and/or R18 and to also provide ameasure of the temperature on the dry side of the substrate viathermister R38. Microprocessor 30 is further programmed to compensatefor anomalies caused by a temperature difference between the wet and drysides of the substrate.

[0046] A temperature difference between the two sides of the substratecan have the effect of expanding one side, while contracting the other.This temperature difference can appear to microprocessor 30 as a changein pressure. In extreme cases, this can cause the controller to turn thepump on or off, independently of an actual pressure reading. In a ‘mild’case, the accuracy of the cut in pressure may be affected. Incombination with other factors, this temperature difference couldpotentially cause the controller (on a low pressure pump) to concludethat no water pressure is present and react to a ‘loss of prime’situation by shutting down the pump unnecessarily.

[0047] The sensor assembly includes pressure sensing means showngenerally at 32 and flow sensing means shown generally at 33. Pressuresensing means 32 includes a bridge circuit containing piezo resistors R9and R10 and operational amplifier U1A. Flow sensing means 33 is based onthermal transfer or loss measurement principles as described herein andincludes a bridge circuit containing thermisters R1 and R2 andoperational amplifier U1B. The sensor assembly includes a triac drivefor switching on a pump motor (not shown) and manual override/resetmeans shown generally at 36 and an LED alarm shown generally at 37.

[0048] The sensor assembly includes a heater for flow sensing means 33designated by resistor R26 and a power supply shown generally at 38.

[0049] Microprocessor 30 may be programmed to capture or log operationaldata including key values of such data, over a period of time, such asthe past 20 days. The logged data may include, the number of pumpstarts, operating voltage, etc. The logged data may serve as adiagnostic tool to facilitate fault location in the event of a servicecall or the like. For example, so called brown outs due to low supplyvoltages, particularly in remote installations, are a common cause ofsome failures.

[0050]FIG. 4 shows a cross section through the sensor housing includinga seal assembly protecting the dry side 40 of sensor substrate 11. Theseal assembly includes a high-pressure seal comprising a peripheral bead41 interposed between the wet side 42 of substrate 11 and the peripheralinner edge 43 of the sensor housing adjacent flow sensing opening 50.Peripheral bead 41 is compressed by pressure applied to substrate 11 viaclosure element 44 associated with the housing.

[0051] A leak path 45 is provided to vent chamber 46, which vent chamber46 is maintained at atmospheric pressure. Vent chamber 46 is insulatedfrom the dry side 40 of sensor substrate 11 via a secondary seal whichforms part of the seal assembly. The secondary seal comprises aperipheral bead 47 interposed between a peripheral edge associated withvent chamber 46 and closure element 44. Bead 47 is compressed bypressure applied via closure element 44. Closure element 44 is fixed tothe main body of the sensor housing by screws or the like. Beads 41 and47 are formed from an elastomeric material and connected by membrane 48formed from a similar material. Membrane 48 provides an additionalbarrier to moisture reaching the dry side of substrate 11. Membrane 48is substantially S-shaped in cross-section and includes recess 49 shapedto receive the peripheral edge of substrate 11.

[0052]FIG. 5 shows a view from the wet side of a practical embodiment ofsensor substrate 11 mounted within a seal assembly 51.

[0053]FIG. 6 shows a view from the dry side of sensor substrate 11mounted within the seal assembly 51. FIG. 6 clearly shows conductivetracks 60 and resistors 61 and other components printed onto substrate11.

[0054]FIG. 7 shows electronic components associated with the sensorassembly mounted on the dry side of the sensor substrate 11.

[0055]FIG. 8 shows a view of the main body 80 of the housing for thesensor assembly together with its closure member 44.

[0056]FIG. 9 shows an underside view of closure member 44 including aprojection 81 that is of similar contour to flow sensing opening 50 andis adapted to apply pressure to substrate 11 at least in the vicinity ofthe flow sensing opening 50.

[0057]FIG. 10 is a view of the main housing showing the flow sensingopening 50 nested within vent chamber 46. A peripheral recess 82 adaptedto receive bead 41 of the seal assembly surrounds flow sensing opening50.

[0058]FIG. 11 shows the sensor substrate 11 and seal assembly 51 mountedwithin vent chamber 46 of main body 80 of the housing.

[0059]FIG. 12 shows an underside view of the main body 80 of the housingwith the closure member removed and the flow-sensing opening 50 clearlyshown. A venturi device 83 is included in the vicinity of flow sensingopening 50. Venturi device 83 is shaped approximately like a human earto accelerate the flow of pumped water in the vicinity of opening 50.

[0060] It will be appreciated that various alterations, modificationsand/or additions may be introduced into the constructions andarrangements of parts previously described without departing from thespirit or ambit of the invention.

1. A pump controller for controlling a pump for a fluid medium such aswater, said pump controller including: a metal substrate adapted to havea first side thereof exposed to said fluid medium; an insulating mediumapplied to a second side of said substrate; pressure sensing meansincluding at least one pressure responsive element implemented on saidinsulating medium closely adjacent said substrate such that saidpressure element is responsive to pressure of said fluid medium whensaid first side is exposed to said fluid medium; flow sensing meansincluding at least one source of heat and at least one temperatureresponsive element implemented on said insulating medium closelyadjacent said substrate, such that said temperature responsive elementis responsive to flow of said fluid medium when said first side isexposed to said flow, said fluid medium providing a sink for said sourceof heat in a manner that is related to said flow; switching means forswitching said pump on or off; and processing means for receiving datafrom said pressure sensing means and said flow sensing means, said databeing communicated via conductive tracks implemented on said insulatingmedium, said processing means being adapted for processing said data andfor producing an output for driving said switching means.
 2. A pumpcontroller according to claim 1 wherein said metal substrate includestitanium.
 3. A pump controller according to claim 1 wherein said metalsubstrate includes low carbon stainless steel.
 4. A pump controlleraccording to claim 1, wherein said insulating medium includes a ceramic.5. A pump controller according to claim 1 wherein said pressureresponsive element includes a plurality of resistors formed byconductive tracks on said insulating medium, said resistors beingarranged such that pressure on said substrate is measured by a change invalue due to tension on said resistors.
 6. A pump controller accordingto claim 1 wherein said temperature responsive element includes anoperational amplifier and a bridge circuit containing a plurality ofthermisters.
 7. A pump controller according to claim 1 wherein saidswitching means includes a triac.
 8. A pump controller according toclaim 7 wherein said triac is mounted on said substrate to provide saidsource of heat.
 9. A pump controller according to claim 1 wherein saidat least one temperature responsive element includes a temperaturesensor on each side of said metal substrate for detecting a temperaturedifference between said first and second sides.
 10. A pump controlleraccording to claim 9 wherein said processing means is adapted tocompensate for anomalies caused by said temperature difference.
 11. Apump controller according to claim 1 wherein said processing meansincludes a microprocessor or microcontroller.
 12. A housing for a sensorsubstrate having a wet side and a dry side and adapted to promotecontact of said wet side with a fluid medium and to substantiallyprevent contact of said dry side with said fluid medium, said housingincluding: a main body having an opening for said fluid medium and forreceiving said sensor substrate with its wet side exposed to saidopening; a first chamber maintained substantially at atmosphericpressure; first sealing means arranged between said opening and saidsensor substrate such that a leak path is provided to said firstchamber; a closure for said housing including a second chamber exposedto said dry side of said sensor substrate; and second sealing meansarranged between said closure and said first chamber to substantiallyprevent ingress of said fluid medium to said second chamber.
 13. Ahousing according to claim 12 wherein said first sealing means includesa peripheral bead interposed between said wet side of said sensorsubstrate and an inner edge of said opening.
 14. A housing according toclaim 12 wherein said second sealing means includes a peripheral beadinterposed between an edge associated with said first chamber and saidclosure.
 15. A housing according to claim 12 wherein said first andsecond sealing means are connected by a membrane, said membraneproviding an additional barrier to moisture reaching said dry side ofsaid sensor substrate.
 16. A housing according to claim 15 wherein saidmembrane includes a recess for receiving a peripheral edge of saidsensor substrate.
 17. A housing according to claim 12 wherein said firstand second sealing means are formed from an elastomeric material.
 18. Ahousing according to claim 12 wherein said membrane is formed from anelastomeric material.
 19. A housing according to claim 12 including aventuri device adapted to accelerate flow of pumped fluid in thevicinity of said opening.
 20. A pump controller adapted for controllinga pump for a fluid medium substantially as herein described withreference to FIGS. 1 to 3 of the accompanying drawings.
 21. A housingfor a sensor substrate substantially as herein described with referenceto FIGS. 4 to 12 of the accompanying drawings.